Interactions between β-cyclodextrin and an amino acid-based anionic gemini surfactant derived from cysteine

Area of Science:

• Supramolecular Chemistry
• Colloid and Surface Science

Background:

• Beta-cyclodextrin (β-CD) is a cyclic oligosaccharide known for its ability to form inclusion complexes.
• Gemini surfactants, like the amino acid-based C(8)Cys(2), exhibit unique aggregation properties.
• Understanding host-guest interactions is crucial for designing advanced materials and formulations.

Purpose of the Study:

• To investigate the inclusion complexation between β-CD and an anionic gemini surfactant (C(8)Cys(2)).
• To determine the binding stoichiometry and affinity of the β-CD-gemini surfactant complex.
• To elucidate the effect of complexation on the micellization behavior of the gemini surfactant.

Main Methods:

• Electrical conductivity measurements.
• UV-Vis spectral displacement technique using phenolphthalein.
• (1)H Nuclear Magnetic Resonance ((1)H NMR) spectroscopy.

Main Results:

• Evidence for the formation of a 1:1 inclusion complex between β-CD and C(8)Cys(2).
• Consistent binding constant (K(1)) values of approximately 10(2) dm(3) mol(-1) obtained from all techniques, indicating weak binding.
• An increase in β-CD concentration shifted the apparent critical micelle concentration (cmc(∗)) to higher values, suppressing micelle formation.

Conclusions:

• The study confirms the formation of a weak 1:1 inclusion complex between β-cyclodextrin and the cysteine-derived gemini surfactant.
• The presence of β-CD significantly influences the micellization process by reducing the availability of free surfactant monomers.
• These findings provide insights into the molecular interactions governing cyclodextrin-surfactant systems, relevant for applications in drug delivery and formulation science.